Bath tub closures are of two basic types, trip lever and non-trip lever. A trip lever closure consists of a stopper connected by means of a linkage system to a trip lever handle mounted on the front end wall of the tub. The closure is opened and closed by raising or lowering the trip lever. The trip lever is susceptible to mechanical failure especially in high usage environments such as hotels.
Non-trip lever closures such as the push-pull drain closures disclosed herein require direct contact with a hand or foot to open and close and are less susceptible to mechanical failure. A disadvantage of some push-pull closures is that they are susceptible to pilfering in hotel usage. U.S. Pat. Nos. 4,926,507, 4,908,883 and 4,720,877 disclose push-pull drain closures made with threaded center posts to reduce pilfering. In U.S. Pat. Nos. 4,926,507 and 4,720,877, the center post is made with a metal spring element that provides the friction necessary to maintain the stopper portion of the drain closure in the desired position relative to the center post. The metal to metal contact during operation of these devices makes the up and down stopper action rough and scratchy. Although the drain stopper disclosed in U.S. Pat. No. 4,908,883 avoids this disadvantage by using elastomeric O-rings as frictional holding members, the soft O-rings degrade much more rapidly, necessitating more frequent replacement.
A center post drain closure is, therefore, needed that is both smoothly operating and resistant to wear and chemical attack.